On Wed, Mar 23, 2016 at 1:10 PM, Brad Templeton <bradtem@xxxxxxxxx> wrote: > It is Ubuntu wily, which is 4.2 and btrfs-progs 0.4. I will upgrade to > Xenial in April but probably not before, I don't have days to spend on > this. Is there a fairly safe ppa to pull 4.4 or 4.5? I'm not sure. In olden days, I > would patch and build my kernels from source but I just don't have time > for all the long-term sysadmin burden that creates any more. > > Also, I presume if this is a bug, it's in btrfsprogs, though the new one > presumably needs a newer kernel too. No you can mix and match progs and kernel versions. You just don't get new features if you don't have a new kernel. But the issue is the balance code is all in the kernel. It's activated by user space tools but it's all actually done by kernel code. > I am surprised to hear it said that having the mixed sizes is an odd > case. Not odd as in wrong, just uncommon compared to other arrangements being tested. > That was actually one of the more compelling features of btrfs > that made me switch from mdadm, lvm and the rest. I presumed most > people were the same. You need more space, you go out and buy a new > drive and of course the new drive is bigger than the old drives you > bought because they always get bigger. Of course and I'm not saying it shouldn't work. The central problem here is we don't even know what the problem really is; we only know the manifestation of the problem isn't the desired or expected outcome. And how to find out the cause is different than how to fix it. > Under mdadm the bigger drive > still helped, because it replaced at smaller drive, the one that was > holding the RAID back, but you didn't get to use all the big drive until > a year later when you had upgraded them all. In the meantime you used > the extra space in other RAIDs. (For example, a raid-5 plus a raid-1 on > the 2 bigger drives) Or you used the extra space as non-RAID space, ie. > space for static stuff that has offline backups. In fact, most of my > storage is of that class (photo archives, reciprocal backups of other > systems) where RAID is not needed. > > So the long story is, I think most home users are likely to always have > different sizes and want their FS to treat it well. Yes of course. And at the expense of getting a frownie face.... "Btrfs is under heavy development, and is not suitable for any uses other than benchmarking and review." https://www.kernel.org/doc/Documentation/filesystems/btrfs.txt Despite that disclosure, what you're describing is not what I'd expect and not what I've previously experienced. But I haven't had three different sized drives, and they weren't particularly full, and I don't know if you started with three from the outset at mkfs time or if this is the result of two drives with a third added on later, etc. So the nature of file systems is actually really complicated and it's normal for there to be regressions - and maybe this is a regression, hard to say with available information. > Since 6TB is a relatively new size, I wonder if that plays a role. More > than 4TB of free space to balance into, could that confuse it? Seems unlikely. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
